Saw-tooth wave form current and voltage generating device



Sept 1936- 'r. NAKASHIMA ET AL 2,055,611

SAW-TOOTH WAVE FORM CURRENT AND VOLTAGE GENERATING DEVICE Filed Aug.- 1, 1953 q MENTORS.

Patented Sept. 29, 1936 UNITED STATES SAW-TOOTH WAVE FORM CURRENT AND VOLTAGE GENERATING DEVICE Tomomasa. Naliashima and Keniiro Takayanagi, Hamamatsu, Japan Application August 1, 1933, Serial No. 683,117 In Japan December 29, 1932 4 Claims.

This invention relates to a device for generating saw tooth wave form current or voltage which may be used for deflecting the electron passage in a cathode ray tube used for television systems and cathode ray oscillographs, and its principal object is to provide a simple and effective device whereby the most desirable saw tooth shaped current or voltage adapted for energizing an electromagnetic or electrostatic deflecting means of a cathode ray tube may be easily obtained.

There have, heretofore, been proposed several devices for generating saw tooth wave form currents or voltages adapted to be used for deflecting the cathode ray in a cathode ray tube utilized.

for television art and cathode ray oscillographs. Among such devices, it has been found that a saw tooth wave form current generator comprising a condenser connected to a direct current source through a high resistance, a short circuiting vacuum valve connected to opposite terminals of the condenser, and a constant frequency oscillator for controlling the short circuiting vacuum valve could produce accurate saw tooth shaped currents and voltages. The device, however, has disadvantages of complicated connections which can not be easily adjusted.

In accordance with this invention, accurate saw tooth shaped voltages and currents can be obtained by using and specially connecting a single vacuum valve having two or more grids, such as a pentode valve, as the combined oscillator and short circuiting device of a condenser.

This invention will be better understood from the following description taken in connection with the accompanying drawing, Fig. 1 of which is a diagrammatic representation of a saw tooth voltage generating device embodying this invention, while Fig. 2 shows curves for illustrating the operation of this invention.

Referring to Fig. 1, in accordance with this invention, we made use of a pentode vacuum valve 2 as an oscillator and short circuiting device of a condenser I which is connected to the main grid circuit of the next amplifying pentode vacuum valve l3 to generate saw tooth shaped electric currents. The opposite terminals of the condenser I connected to a direct current source A through a resistance 3 are short clrcuited. by the plate circuit of the pentode or multi-grid vacuum valve 2. The oscillation and short circuiting vacuum valve 2 should preferably be a pentode valve provided with a plate, a filament 2', a main grid or control grid 4, an auxiliary grid or a screen grid 5 and an earth grid 6 which is connected directly to the filament 2'. The main grid 4 of the oscillator valve is connected to the ills.- ment 2' through an oscillation coupling coil 1 and an oscillation element comprising a condenser 8 and a high resistance 9 connected in shunt thereto.

The auxiliary grid 5 of the oscillation and short circuiting valve 2 is connected to the intermediate tap of the direct current source A through another coupling coil in, the negative side of the source A being led to the filament 2 of said pentode valve 2. The oscillation coupling coils I and I should be wound cumulatively on a common iron core i0, and it is desirable that their distributed capacities may be as small as possible. The opposite terminals l l and Hot the condenser I, that is, the plate and the filament 2 of the pentode vacuum valve 2 are directly connected to the main grid circuit of the amplifying pentode valve l3. The plate circuit of the pentode valve I3 is connected to an electromagnetic 0011 I4, which; for instance, is mounted to a cathode ray tube B for deflecting the electron stream thereof. I and I6 represent the common B-battery of the plate and the auxiliary grid and the grid biasing source of the main grid of the pentode valve 13 respectively.

In the above described arrangement, the condenser is normally charged'at a constant rate from the direct current source A. It is assumed that the oscillation and short circuiting pentode valve 2 becomes initially conductive because of the same potential of the main grid 4 and the filament 2'. Then the current will pass through the circuit of the coupling coil ill with the result that the potential large enough to maintain the main grid 4 sufliciently negative with respect to the filament 2'- will be induced in the coupling coil I. This bias voltage is accumulated in the grid condenser 8 with the positive polarity at the left hand terminal and with the negative polarity at its right hand terminal in Fig. 1. At this moment the current through the coupling coil ID will be stopped and there occurs no transformer action between the coupling coils l and Ill. The accumulated charge of the condenser 8 should be gradually discharged through the high resistance 9 for the predetermined period T. At the very moment that the period is over and the main grid 4 is recovered to the initial condition with respect to the filament 2', the next impulsive current will flow through the circuit of the coupling coil l0, and the oscillation just described above will be continued. Thus the oscillation and short circuiting pentode valve 2 will produce continuous but impulsive oscillation in response to the electromagnetic regenerative action between the oscillation coupling coils I, I and by the charge and discharge action of the oscillation element comprising the high resistance 9 and the condenser 8. The period T of the oscillation can be determined by adjusting the resistance 9 or the condenser 8. That is, the impulsive current having the wave form a with the period T as shown in Fig. 2 will pass through the circuit comprising the auxiliary grid and coupling coil l0, and at the same time the current of-the wave form b tends to flow through the plate circuit of the valve 2. At this moment the valve 2 becomes conductive so that the condenser l which is normally charged from the direct current source A through the resistance 3 will be short circuited by this valve 2. Accordingly it is easily understood that the saw tooth shaped current or voltage 0 as shown in Fig. 2 is produced between the terminals II and I2. The saw tooth current 0 thus produced may be amplified by the pentode vacuum valve l3 and utilized for deflecting the electron passage in the cathode ray tube. Although the pentode vacuum valve 2 is employed as the combined oscillation and short-circuiting valve in the example illustrated herein, yet the object of this invention may be obtained equally well by using a different vacuum tube, such as a screened grid valve having electrodes corresponding to the main grid 4 and the auxiliary grid 5 of the mentioned pentode valve 2.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. A device for generating a current and voltage of saw tooth wave form comprising a vacuum valve provided with a filament, a main grid, an auxiliary grid, an earth grid directly connected to said filament, and a plate, a condenser connected to a direct current source in order to be charged therefrom through a resistance and inserted between the plate and the filament of said .vacuum valve so as to be short circuited thereby,

an oscillation coupling coil connected between the main grid and the filament of said vacuum valve, an oscillation element consisting of a resistance and a condenser connected in shunt thereto and in series with said oscillation coupling coil, and another oscillation coupling coil connected between the auxiliary grid and the filament of said vacuum valve through a direct current source to cooperate with said first mentioned oscillation coupling coil.

2. A device for generating a current and voltage of saw tooth wave form comprising a pentode vacuum valve provided with a filament, a control grid, a screen grid, an earth grid and'a plate, a condenser connected to a direct current source in order to be charged therefrom through a high resistance and inserted between the plate and the filament of said pentode vacuum valve, an oscillation coupling coil connected between the control grid and the filament of said pentode vacuum valve, an oscillation element consisting of a resistance and a condenser connected in shunt thereto and connected in series with said oscillation coupling coil, and another oscillation coupling coil connected between the screen grid and the filament of said pentode vacuum valve through a direct current source so as to cooperate with said first mentioned oscillation coupling coil, said oscillation coupling coils being wound cumulatively on a common iron core and the earth grid of said pentode vacuum valve being connected directly to the filament thereof.

3. A device for generating a current and voltage of saw tooth wave form comprising, in combination, a vacuum valve provided with a filament, a control grid, a sc een grid and a plate, a resistance, a condenser connected to a direct current source in order to be charged therefrom through said resistance and inserted between the plate and the filament of said vacuum valve so as to be short circuited thereby, an oscillation coupling coil connected between the control grid and the filament of said vacuum valve, an oscillation element consisting of a resistance and a condenser connected in shunt thereto and connected in series with said oscillation coupling coil, and another oscillation coupling coil connected between the screen grid and the filament of said vacuum valve through a direct current source so as to cooperate with said first mentioned oscillation coupling coil.

4. A device for generating a current and voltage of saw tooth wave form comprising a vacuum valve provided with a filament, a control grid, a screen grid and a plate, a resistance, a condenser connected to a direct current source in order to be charged therefrom through said resistance and inserted between the plate and the filament of said vacuum valve so as to be short circuited thereby, an oscillation coupling coil connected between the control grid and the filament of said vacuum valve, an oscillation element consisting of a variable resistance and a variable condenser connected in shunt thereto and connected in series with said oscillation coupling coil, and another oscillation coupling coil connected between the screen grid and the filament of said vacuum valve through a direct current source so as to cooperate with said first mentioned oscillation coupling coil, said oscillation coupling coils being wound cumulatively on a common iron core, and thus producing the impulsive and continuous oscillation of any desired frequency by adjusting the electric constant of said oscillation element.

TOMOMASA NAKASHIMA. KENJIRO TAKAYANAGI. 

